Got a heating issue

Dave0176

Customer called for no heat, when I got there the boiler would only run for a min or two, I happend to bump into the pressuretrol and it came on so removed it and cleaned it as it was clogged. I also noticed it was set at 5 psi and 2 on the dial.

Ok a little bit of info, it's a Dunkirk 150,000 386 sq ft boiler installed in 1998. I measured radiation and came up with 190 EDR, so this boiler is waaaay oversized. The boiler is piped wrong, one 2" tapping all in copper, the riser goes straight up into the main, the equilizer is piped off the riser on vertical tee, and obviously this boiler has never been skimmed. The one main vent looked to be about 70 years old wasn't working at all, so I replaced with two No 2 Gortons, now the main heats up nice and quick. I also calculated all the air for the radiators and replaced the vents, then lowered the pressuretrol to .05 and 1. Problem now is the boiler turns off on pressure too quickly. So up had to go the pressuretrol again the home owner actually turned it back up I later after I left because he said he had no heat. Is there anything that can be done short of replacing the boiler, which they won't go for?

Dave0176

Hatterasguy said:

Presuming it is gas based upon the 150K size, it's certainly wise to consider a two stage gas valve for it.

I had thought about that, I also suggested repiping but they won't go for that either. He seems content with leaving the pressure up.

Captain Who

Something else is wrong if it won't heat the radiators with a 0.5 (0.05 typo?) psi cut-in and 1.5 psi cut-out. Has the proper operation of the pressuretrol been verified with a low pressure gauge?

KC_Jones

On my old Weil Mclain I actually ran it for over 10 years with 2 burners completely removed....and it didn't cost me a single penny to do it.

Dave0176

Pics

KC_Jones

In addition to possibly down firing would they go for a partial re-pipe? Maybe at least get the pipe size and equalizer fixed? Oops didn't see your no re pipe comment.

KC_Jones

He sounds like the type that no matter what you say they don't understand that he can pay you some money now to fix it or spend a ton more over time to not fix it. Does the customer actually want anything done to fix the problem?

icesailor

It was done all wrong in the first place. The owner was BS'ed into living with it that way. When there's a problem, and someone who knows what they are doing and how to improve it, is treated with suspicion as a rip off artist.

He's smart. You (and us) are not.

Might be time to wish this place. "Health, Happiness and Long Distance".

The issue of removing burners has merit. I saw it a few times but didn't understand the reasoning because they were all on hot water boilers. I understand the reasoning behind it with steam. I doubt the owner would give you the time to listen to any reason. He's probably getting his technical support from the Internets. Some person that makes video's on the Youse Tubes.

Captain Who

So the consensus is that the steam is so wet here, due to the bad boiler piping, that it takes an inordinate amount of pressure to heat the radiators sufficiently to heat the rooms? Are the radiator vents closing off on steam contact or due to prolonged heating of the radiators with wet steam and trapped air that eventually conducts to the vents and shuts them off?


Are the radiators simply too small for the rooms and for the building heat losses (insulation?)? Putting higher pressure steam into the radiators increases the temperature of the steam and the mass of steam is greater also, so more heat output after shutdown.

Captain Who

5 psi isn't an inordinate amount of pressure? I thought the empire state building only used 2 psi or something. The customer only seems to get satisfactory heat by cranking up the pressuretrol, which should not be necessary if everything was right.

As far as the long boiler run times to get the stat to satisfy, well that certainly "could" be from radiators that are too small for the heat loss on the building at that given time, as well as wet steam instead of the proper dry steam which has higher heating value when it condenses.

Having said all that though, I feel there is not enough information given here so until we know more I won't speculate anymore.

Captain Who

It was this that made me think that:

"I also calculated all the air for the radiators and replaced the vents, then lowered the pressuretrol to .05 and 1. Problem now is the boiler turns off on pressure too quickly. So up had to go the pressuretrol again the home owner actually turned it back up I later after I left because he said he had no heat.

Short cycling on the pressuretrol between 0.5 and 1.5 should not prevent the building from heating. It certainly doesn't in mine with a 46% oversized boiler. It seems like the customer has to overdrive the radiators with hotter higher pressure steam. Dan talks a lot about that in his books.

But I'm not going to keep trying to figure this out with insufficient information having been given us.

Fred

Did anyone ever check the gas pressure/supply to make sure the burner is running within specs?
EDIT: I guess I should have read the entire string first. Clearly if it is cutting out on pressure, the burner is doing it's job.

KC_Jones

This particular boiler is 100% over sized. This seems pretty straight forward to me. Bad piping making wet steam which is probably generating some amount of pressure on the boiler due to all that water not having any place to go (no way it is making it into that equalizer). In addition the boiler is generating steam at a rate at least twice what the system can condense it at. So the boiler short cycles so much at a low pressure setting it takes forever to get some amount of heat into the building. The customer turned it up so that the boiler would run longer on a heating cycle and is probably satisfying the thermostat before it starts cycling on pressure to the point "no heat" is being delivered. With an EDR of 190 we are talking about a really small house here. I would guess something around 1000 sq ft max, probably smaller. If the run time is so short at low pressure you could conceivable continuously condense in the basement and never get steam into the rads. I don't see any insulation on those pipes. Just my $.02

Fred

If He's happy with the pressure up and the way it operates, what's the problem? He's happy. It's the service tech that isn't and he is not in a position to make the install right unless he's will to do it for free. Let it go and let's give advice where it will be received. It's all good!

Captain Who

PV = nRT where P = absolute pressure and T = absolute temperature. Heat transfer is pretty much proportional to temp difference. T = PV/nR or T1/T2 = P1/P2. P1 = 1.5psi + 14.696 psi = 16.196 psi. P2 = 5psi + 14.696 psi = 19.696. T2/T1 = 19.696/16.196 = 1.22 or 22% more heat transfer rate. But that'd be if it were a closed vessle which it isn't, so since the density will be higher with the higher pressure there may not be a heck of a lot of difference.

The greater mass densityand adds to the amount of energy stored within each radiator AFTER the tstat shuts off, which is still available to transfer to the room air. That is probably the main factor here.

Dave0176

I'm going to try and convince a repipe, thinking 2-1/2 riser into a 3" drop header and piping is right, at least this will help, and I'll see about removing a burner or two.

Jamie Hall

Captain Who -- sorry old boy, but "T" in the Universal Gas Equation is the absolute temperature (Rankine or Kelvin)...and saturated steam doesn't conform to the UGT anyway.

But there must be other problems with this set up. Besides being piped all wrong and so on and on.

Me? I'd walk away from it.

Captain Who

OK Saturated Steam:

5 psig = 19.696psia: Sat. Steam Temp = 381.542 K, Latent Heat = 960.652 Btu/lb, Specific Volume = 20.3788 cu ft/lb

1.5 psig = 16.196psia: Sat. Steam Temp = 375.871 K, Latent Heat = 967.189 Btu/lb, Specific Volume = 24.471 cu ft /lb

So Heat Xfer Ratio @ 70 F amb. = (381.542-294.261)/(375.871-294.261) = 1.069, so heat transfer rate = 6.9% greater

Latent Heat Ratio = (960.652/20.3788)/967.189/24.471) = 1.193, So energy storage in radiator = 19.3% greater.

Dave0176

Two rads have been removed, one rad was added to an old porch converted to part of the living room, it's steel piped baseboard 1-1/4 x about 6' long, kitchen rad was removed and replaced with the same type baseboard. The cast iron rads are 10 section tube type 5 tubers this house is only about 1000 sq ft.
Unfortunately the owner is recovering from pancreatic cancer and getting chemo treatments so he likes the heat, and he explained that's why he turned the pressure back up.

Fred

Wow, Wow, Wow, tough position to be in.

vaporvac

Is a two stage gas valve out of the question then? I expect the high pressure setting allows the burners to stay on long enough to statisfy the Tstat. It would probably do it eventually at one psi, but this must be major short cycling.

Captain Who

Still too much missing information about how the tstat is cycling and pressuretrol is cycling, whether radiators are heated all the way across, how the water in the sight glass is behaving while steaming, whether the radiation is sufficient for the house size and heat loss, etc. etc. I wish the owner all the best, that is a tough circumstance to deal with.

Dave0176

Captain Who said:

Still too much missing information about how the tstat is cycling and pressuretrol is cycling, whether radiators are heated all the way across, how the water in the sight glass is behaving while steaming, whether the radiation is sufficient for the house size and heat loss, etc. etc. I wish the owner all the best, that is a tough circumstance to deal with.

Thanks I know the owner a long time, his son and I are friends for over 25 years, so I'm doing the best I can for him within his guidelines.

As far as the radiators heating, after I left he said the radiators didn't get good heat?? So he turned the pressure up and now they super hot. His other son had told me he gets woken in the night because the vent cycles on and off and he said the air blows out if them really hard and loud, and I told him because the pressure is too high.

My thinking is this, at the lower pressure setting the main fills with steam quick since i changed the main vents, but it also fills with pressure too quick shutting down the burner, since the vents aren't hot enough to close the collapsing steam sucks air back in thus creating a circle?? I don't know just a thought.

Fred

Yep, I post this on another string. Sounds like the same issue:

The real issue he has (and one that I experience occassionally) is actually during a situation where the boiler short cycles on pressure as a result of a set back or , in my case, the outside temp and wind is minus 10 or lower.
During that short cycling, there is a small vacuum created at the radiator,when the boiler shuts down that is enough to pull those radiator vents open but not enough to pull the Main vents open and because the Mains are so hot, they vents really don't have a chance to breath during that 2 - 3 minutes before the boiler kicks back on and makes steam again which leaves any air that was sucked in to have to be expelled by the radiator vents that were pulled open and are now cool as a result of sucking that room temperature air in for a couple minutes.

Captain Who

"at the lower pressure setting the main fills with steam quick since i changed the main vents, but it also fills with pressure too quick shutting down the burner, since the vents aren't hot enough to close the collapsing steam sucks air back in thus creating a circle??"

I just don't see how you can get enough pressure to hit the cut-out of 1.5psig, let alone 5 psig, without having the vents be closed. I can't get past that because it is so out of my own experience of what is possible.

ChrisJ

The high pressure is likely due to carry over. As I noticed with too much treatment water blowing into the header will raise the boiler pressure.

It's taking that much pressure to get the steam out of the boiler and that thing someone thought was a header.

Think about blowing air through a tiny hole. As water and or water spray fills the risers it's restricting them.

This could be caused by dirty water or bad piping or both. From the pictures I'd say the piping needs to be fixed for sure and who knows about the quality of the water.

Captain Who

I appreciate the explanation. I think your example proves that there can be a measurable effect. You had about 4.6 oz/sq in of pressure but this is 5 to 17 x that. Just not sure about that.

ChrisJ

Captain Who said:

I appreciate the explanation. I think your example proves that there can be a measurable effect. You had about 4.6 oz/sq in of pressure but this is 5 to 17 x that. Just not sure about that.

I don't know, I think it's possible.
Either that, or all of his vents are terribly slow and the boiler keeps cycling so often it takes forever to actually get heat.

Captain Who

If someone's boiler water is so fouled with oil it might be possible to be throwing a lot of condensate, not only into the riser and mains, but also into the pigtail that the ptrol is mounted on. The two could possibly combine to cause that amount of pressure. Like we decided last night, if the slug of water gets added to by condensate, the gauge or ptrol sees that as additive pressure, even if there is not real change in pressure in the boiler. If there is also a backpressure in the boiler due to all that condensate in the riser, maybe you could get enough of a problem at the ptrol to cause it to cycle before any steam has really filled the radiators and with vents still open. Not sure still.

RobG

As much as I hate to say it, barring a re-pipe you could correct the piping with a copper tee, two 45's and a 90. It would still be copper but it would be a place to start.

Dave0176

I went back to do a thorough cleaning, took some as it was super dirty, added stem master tabs and the freaking water turned black, had to do two more blow downs to get the water even close to decent, so I flushed the returns the boiler a few more times had it acceptable so I added more steam master tabs and it stayed pretty decent. Owner has told me it's running good even at the low pressure setting. Never woulda thought that boiler was that dirty he does take water from it often and the sight glass was not too bad.

JStar

Always suspect dirt.

And never remove burners from a boiler. You'll cause unwanted thermal stress on the boiler sections, and could possibly disturb the combustion process, which may produce unhealthy amounts of CO.